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/*
 * Javassist, a Java-bytecode translator toolkit.
 * Copyright (C) 1999- Shigeru Chiba. All Rights Reserved.
 *
 * The contents of this file are subject to the Mozilla Public License Version
 * 1.1 (the "License"); you may not use this file except in compliance with
 * the License.  Alternatively, the contents of this file may be used under
 * the terms of the GNU Lesser General Public License Version 2.1 or later,
 * or the Apache License Version 2.0.
 *
 * Software distributed under the License is distributed on an "AS IS" basis,
 * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
 * for the specific language governing rights and limitations under the
 * License.
 */

package com.feilong.lib.javassist.bytecode;

import java.io.ByteArrayOutputStream;
import java.io.DataInputStream;
import java.io.IOException;
import java.util.Map;

import com.feilong.lib.javassist.CtClass;
import com.feilong.lib.javassist.bytecode.annotation.AnnotationsWriter;
import com.feilong.lib.javassist.bytecode.annotation.MemberValue;

/**
 * A class representing AnnotationDefault_attribute.
 *
 * 
 * For example, if you declare the following annotation type:
 *
 * 
 * @interface Author{
 * 
 *     String name() default "Shakespeare";
 * 
 *     int age() default 99;
 * }
 * 
 *
 * 
 * The defautl values of name and age
 * are stored as annotation default attributes in Author.class.
 * The following code snippet obtains the default value of name:
 * 
 * 
 * ClassPool pool = ...
 * CtClass cc = pool.get("Author");
 * CtMethod cm = cc.getDeclaredMethod("age");
 * MethodInfo minfo = cm.getMethodInfo();
 * AnnotationDefaultAttribute ada
 *         = (AnnotationDefaultAttribute)
 *           minfo.getAttribute(AnnotationDefaultAttribute.tag);
 * MemberValue value = ada.getDefaultValue());    // default value of age
 * 
 *
 * 
 * If the following statement is executed after the code above,
 * the default value of age is set to 80:
 *
 * 
 * ada.setDefaultValue(new IntegerMemberValue(minfo.getConstPool(), 80));
 * 
 *
 * @see AnnotationsAttribute
 * @see com.feilong.lib.javassist.bytecode.annotation.MemberValue
 */

public class AnnotationDefaultAttribute extends AttributeInfo{

    /**
     * The name of the AnnotationDefault attribute.
     */
    public static final String tag = "AnnotationDefault";

    /**
     * Constructs an AnnotationDefault_attribute.
     *
     * @param cp
     *            constant pool
     * @param info
     *            the contents of this attribute. It does not
     *            include attribute_name_index or
     *            attribute_length.
     */
    public AnnotationDefaultAttribute(ConstPool cp, byte[] info){
        super(cp, tag, info);
    }

    /**
     * Constructs an empty AnnotationDefault_attribute.
     * The default value can be set by setDefaultValue().
     *
     * @param cp
     *            constant pool
     * @see #setDefaultValue(com.feilong.lib.javassist.bytecode.annotation.MemberValue)
     */
    public AnnotationDefaultAttribute(ConstPool cp){
        this(cp, new byte[] { 0, 0 });
    }

    /**
     * @param n
     *            the attribute name.
     */
    AnnotationDefaultAttribute(ConstPool cp, int n, DataInputStream in) throws IOException{
        super(cp, n, in);
    }

    /**
     * Copies this attribute and returns a new copy.
     */
    @Override
    public AttributeInfo copy(ConstPool newCp,Map classnames){
        AnnotationsAttribute.Copier copier = new AnnotationsAttribute.Copier(info, constPool, newCp, classnames);
        try{
            copier.memberValue(0);
            return new AnnotationDefaultAttribute(newCp, copier.close());
        }catch (Exception e){
            throw new RuntimeException(e.toString());
        }
    }

    /**
     * Obtains the default value represented by this attribute.
     */
    public MemberValue getDefaultValue(){
        try{
            return new AnnotationsAttribute.Parser(info, constPool).parseMemberValue();
        }catch (Exception e){
            throw new RuntimeException(e.toString());
        }
    }

    /**
     * Changes the default value represented by this attribute.
     *
     * @param value
     *            the new value.
     * @see com.feilong.lib.javassist.bytecode.annotation.Annotation#createMemberValue(ConstPool, CtClass)
     */
    public void setDefaultValue(MemberValue value){
        ByteArrayOutputStream output = new ByteArrayOutputStream();
        AnnotationsWriter writer = new AnnotationsWriter(output, constPool);
        try{
            value.write(writer);
            writer.close();
        }catch (IOException e){
            throw new RuntimeException(e); // should never reach here.
        }

        set(output.toByteArray());

    }

    /**
     * Returns a string representation of this object.
     */
    @Override
    public String toString(){
        return getDefaultValue().toString();
    }
}